1. Field of the Invention
The present invention relates to an antenna device, and more particularly, to an antenna device capable of performing dual-band operation and substantially being directional in a high-frequency band and omnidirectional in a low-frequency band.
2. Description of the Prior Art
As the communication techniques progress, many wireless communication systems support dual-band operations. To achieve the dual-band operation, the prior art have to respectively manufacture antennas for high/low-frequency operations, and combine the antennas with a duplexer as an antenna device. However, the gain of the antenna device reduces dramatically and has reliability issues if the antenna device is minimized.
In addition, the antenna device may need to timely adjust an antenna angle or directional position in some applications, which may result in signal dead zones during the adjustment. For example, indoor customer premises equipments are utilized to provide indoor wireless communication services. Since indoor partitions and furniture placements may affect the propagation of wireless electric waves, the prior art has provided an antenna device capable of automatically adjusting the antenna angle or directional position, such that the indoor customer premises equipments may adjust transmitting and receiving conditions of wireless signals according to distribution of indoor users. However, when the antenna device is adjusting the antenna angle or directional position, signal dead zones may occur, which affects utilization and causes inconvenience if there are users in the signal dead zones, or the adjustment is too slow.
Therefore, how to improve a gain of a minimized dual-band antenna and how to avoid the signal dead zone of the antenna device capable of adjusting the antenna angle or directional position during the adjustment have become critical issues in the field.